Keeping an older, or “aging,” aircraft airworthy is a balancing act of sorts. On one hand, its nice to simply replace rather than repair parts and components when they go bad. On the other had, and since some parts and components are increasingly rare, the cost of changing them out can be stratospheric. The balancing comes-at least for me-from deciding what to replace and what to repair. If I replaced every part or component presenting an issue, instead of repairing it, Id have no money left over to use for other parts and components. Or to fly the darn thing in the first place. Its no huge secret that many parts installed on older aircraft are generic automobile components from the era in which they were first designed. Items such as window cranks, ashtrays and the like certainly qualify, but so do many electrical components like relays and even generators. Parts like light bulbs and cabin speakers frequently can (and perhaps should) be replaced with a modern equivalent. Discussing modern lubricants is an entirely different subject, as is the “owner-produced” part. Meanwhile, operators of older aircraft often will find themselves needing, say, a new generator only to discover it is no longer available from traditional sources. Scrounging then becomes the order of the day, perhaps for a rebuilt example. Eventually, the scrounger will discover the generator was first used on, for example, a 46 Buick and some guy in Arkansas has a warehouse full of them hed be happy to sell. The only problem is they dont have the right part number or are missing a special diode. The situation then becomes one of convincing the FAA-certificated technician doing the work to sign off on the obviously identical-but-unapproved part. Often, theres no downside, as long as all parties to such a transaction know what theyre doing. The lack of a downside can also depend on the type of component involved. But such a decision should never be taken lightly-in our generator example, it might be a good time to upgrade to an aftermarket alternator-based system. The point of all this is to remind owners/operators they are the ones responsible for ensuring airworthiness. Further, let us stretch the bounds of understatement: Installing an unapproved or simply incorrect part in a critical aircraft system can have undesirable consequences, as the following demonstrates. Background On May 7, 2007, at about 1146 Mountain time, a Cessna P210N was substantially damaged when it collided with terrain during an emergency approach and landing in Spanish Fork Canyon, Utah. The solo private pilot was killed. Visual conditions prevailed and an IFR flight plan was in effect for the flight. At 1140:14, the pilot advised ATC the airplane had a rough-running engine; he subsequently reported a fire. Approximately five minutes after the first report of trouble, the pilot stated he had to land. Multiple witnesses reported seeing the airplane flying northwest through the canyon at low altitude and trailing smoke. Witnesses described the airplane flying a left downwind and base to a pasture, and reported the airplane impacted terrain while in a steep left-hand turn. The airplane was fully engulfed by a post-crash fire shortly afterward. Investigation The airplane came to rest at the end of a 200-foot-long debris field at an elevation of about 4884 feet MSL. All major aircraft components and flight controls were identified at the crash site. Extensive fire, impact damage and fragmentation were noted. A black oil-like substance was noted on right horizontal stabilizers leading edge. The landing gear and flaps were retracted and the speed brakes were stowed. The engine assembly was largely intact; no evidence of an uncontained engine failure was noted. Heavy dark soot and oil deposits were visually observed on the bottom of the engine, starting inboard of the number-six (front left) cylinder and extending aft to the accessory section. Oil deposits were also observed on the turbo charger wastegate actuator oil inlet hose. Additional examination of the wastegate oil inlet hose at the B-nut revealed that 4-5 threads were engaged and the B-nut was finger loose. The sooting and oil deposits on the bottom of the engine were prominent on the left side of the crankcase. The deposits were inboard and aft of the wastegate assembly. The airplanes most recent annual inspection was completed on April 17, 2007. Examination of two metal-braided, non-fire-shielded hoses routing engine oil to and from the turbocharger wastegate actuator revealed they both were covered in a dark soot and oil-like substance. In addition, both oil hoses appeared thermally damaged. The wastegate actuator inlet hose was pressure-tested and a leak was noted between the hose collar and the B-nut on the hoses actuator side. The oil return hose was pressure tested and multiple leaks were noted along a 14-inch section. The hoses steel-braided outer cover was removed, and the inside rubber hose was found to be deteriorated and oil soaked. The airplanes logbooks did not contain a specific entry detailing installation of the hoses. A representative from the engine manufacturer stated the steel braided hoses found on the accident airplane were not supplied by the engine manufacturer. Probable Cause The National Transportation Safety Board determined the probable cause of this accident to include, “An engine oil line leak and subsequent engine compartment fire while in cruise flight.” To which we could add, “A contributing factor was the operator or maintenance technicians decision to install substandard components in a critical application.” For years, the FAA has been engaged in a major effort to locate and remove from the inventory various unapproved parts. The parts in question can range from substandard/mislabeled fasteners to engine shops that cut corners and intentionally counterfeit components. Most of the time, the agencys efforts are focused on components for transport-category aircraft. The regulations rightly place on an aircrafts owner/operator the burden of ensuring airworthiness. That responsibility must include judgement: Maybe a hardware-store screw is adequate to secure an armrest to the sidewall; maybe it isnt. It certainly wont be adequate to, for example, attach the prop spinner, or a wingtip. Dont cut corners when buying or installing safety-critical components.
